Pope John Paul II Tuesday arrived in Toronto at the start of a three-nation tour of the Americas by holding up Canada as a model of tolerance and justice for the world.

The frail, 82-year-old leader of the world's 1 billion Roman Catholics arrived in Canada for World Youth Day - a six-day celebration of faith for young people. Speaking to a gathering of dignitaries and invited guests in an airport hangar, the Pope praised Canada as a champion of human rights and human dignity.

"In a world of great social and political extremes, and confusion about the very purpose of life, Canadians have an incomparable treasure to contribute on condition that they preserve what is deep and good and worthy in their own heritage," he said.

This is the pope's third trip to Canada, and his arrival comes at a time when the Catholic Church, particularly the American church, is embroiled in scandals. Organizers say those scandals are one reason this World Youth Day event will likely be the smallest ever - with just 200,000 people attending.

Despite this, the theme of this event that Catholic young people represent the "salt of the earth and light of the world" has attracted participants from 100 countries.

The pope's 11-day trip, which includes stops in Guatemala and Mexico, is likely to be his last overseas mission. The effects of Parkinson's disease have left the pontiff physically weak and struggling when he walks and speaks. Still, as he walked, almost unaided, down the steps from the airplane that carried him to Canada, Pope John Paul II showed his incomparable willpower has not been diminished.

The pope's Toronto trip culminates on Sunday with a mass at an old military airport. But before he attends any events, he will be flown to a Catholic retreat on Strawberry Island, about 100 kilometers north of Toronto.